For cross-site runs between switching networks and antennas, a low-loss alternative to standard WR75 and WR62 has emerged. The Signal Wave System (SWS) promises to provide increased power-handling capabilities compared to traditional waveguides for savings on runs as short as 10 m. For example, a typical standard WR75 40-m run would have a loss of approximately 5.6 dB. Yet an equivalent SWS run will reduce this to only 1.6 dBa savings of 4 dB. This improvement is achieved by adding an electroformed taper transition from WR75 to SWS75 as well as a mode suppressor and a length of over-sized waveguide in the run.

The over-sized section is made from precision-drawn waveguide. It is terminated with special flanges to minimize mismatch in the waveguide run. In SWS installations, the run length is many times the signal wavelength. As a result, the trapped resonant frequencies form comb lines. Even though these higherorder modes are very weak (typically -60 dBc or less), trapped-mode conversion affects linearity whenever the operating frequency coincides with one of the comb lines. The exact process causes small wiggles in the group delay at the comb-line frequencies, which are absorbed by the mode suppressor.

Luso Electronics, 831 Salisbury House, London Wall, London EC2M 5QQ; +44 (0)207 588 1109, FAX: +44 (0)207 638 7674, www.lusoelectronics.com.

See Associated Figure